Walton High School and Oakridge Primary School in Stafford were among those sent the threats, as was Perton School near Wolverhampton and hundreds of other schools around the country.

A message from Walton High School headteacher Neil Finlay posted on the school website today said: "At 10.30 yesterday morning, I received a threatening email which claimed that a car would be driven into our students as they left school in the afternoon at 3.15 pm.

"It also told me that if I tried to evacuate the school, the driver would get out and shoot any student leaving.

"It informed me that I had a choice but that my only way out was to go out with a BANG.

"I immediately telephoned 999 to pass on the information as well as informing my Governing Body.

Advertising

"The email originated, apparently, from the same group who had made hoax bomb threats to many schools across the country last week.

"Many things in the email did not ring true, not least the fact that we do not finish at 3.15 pm.

"However, I clearly wanted to wait for police advice.

"The police were excellent and communicated quickly to all Staffordshire schools.

Advertising

"They advised that the same generic email had been received by many schools across the country and that it presented no credible threat based on their intelligence.

"They advised the following: Do not raise concerns with pupils or create panic amongst building occupants. Remain vigilant and raise any concerns with the police immediately and follow your emergency procedures.

"Therefore, we put a large senior staff presence on all exits and roads around the school at both 3.20 pm when our Year 7 to Year 11 students left and again at 5 pm when our Sixth Form lessons finished.

"I have tried to contact you first thing this morning to reassure you.

"I totally understand that news such as this is extremely concerning but I hope that you are reassured that we have followed police advice to the letter in order to safeguard your children."

In a statement, the National Crime Agency said: "On the evening of Wednesday 28 March, NCA and Hertfordshire Police officers arrested an 18-year-old man in the Abbots Langley area on suspicion of making malicious communications relating to the threatening emails received earlier today by a large number of schools and colleges throughout the UK.

"We understand these threats have caused considerable concern but we do not assess there to be an increased risk to the public.

"We believe this incident is linked to the hoax bomb threat that closed hundreds of UK schools last week.

"As this is a live investigation we are unable to comment further."

Thousands of students were evacuated from Walsall College's four campuses after bomb threats were sent to more than 400 institutions across the UK on March 19.